1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a semiconductor device containing an insulating film having a high dielectric constant, and a method for manufacturing the same.
2. Description of the Related Art
Recently, as the next generation gate insulator replacing an silicon dioxide film (SiO2 film), expectations for high dielectric films such as metal silicate films including an Hf silicate film (HfSiO film) have increased. Since the dielectric constant of the Hf silicate film is higher than that of an SiO2 film, the equivalent oxide thickness (EOT) of the Hf silicate film can be reduced while keeping sufficient physical thickness to suppress leakage current.
To form an effectively thin gate insulator, the dielectric constant of the film is desirably as high as possible. Such a dielectric film can be attained by increasing the amount of Hf in the film. However, an excessively large amount of Hf is reported to cause phase separation and crystallization of a film, increasing leakage current.
To prevent the crystallization, use of an HfSiON film formed by adding N to an HfSiO film has been proposed (M. R. Visocay et al., Appli. Phys. Lett., 80, 3183 (2002)). According to the proposal, it is confirmed that when an HfSiO film and HfSiON film are heat-treated for 60 seconds in an N2 atmosphere, the HfSiO film is crystallized at 1,000° C., whereas the HfSiO film remains in amorphous even at 1100° C.
However, as a result of our investigation, we have found that since an Hf—N bond is not present in the films formed by conventional methods, it is not easy to increase the concentrations of both Hf and N.
Therefore, the ratio (percentage) of Hf/(Hf+Si) of a conventional HfSiON film remains at most about 44%. Therefore, an HfSiON film having a high dielectric constant capable of suppressing crystallinity and leakage current has not yet been realized.
It has been confirmed that the HfSiON film formed by an on-axis sputtering method contains Hf—N bonds in an amount of less than 1%. Therefore, an HfSiON film containing a large amount of Hf cannot be obtained.
As described, it has been difficult to form an HfSiON film having a high dielectric constant, capable of suppressing crystallinity and leakage current.
Under the circumstances, the present invention is directed to providing a semiconductor device having an insulating film formed of a nitrogen-incorporated metal silicate film with a high dielectric constant, capable of reducing leakage current lower than an oxide film, and suppressing crystallinity and also directed to the method for manufacturing such a semiconductor device.